Fabrication of a Ru-NiAl layered double hydroxide-oxidized CNT hybrid catalyst for the selective oxidation of benzyl alcohol to benzaldehyde

A NiAl layered double hydroxide-oxidized CNT (NiAl-LDH-o-CNT) hybrid was synthesized by a mild hydrothermal method using o-CNTs, Al(NO₃)₃·9H₂O and Ni(NO₃)₂·6H₂O as the precursors. It was impregnated with RuCl₃ as a catalyst for the oxidation of benzyl alcohol to benzaldehyde and its activity compared with NiAl-LDHs and o-CNTs. The crystal structure and morphological characteristics of the NiAl-LDH-o-CNTs hybrid were characterized by XRD and TEM. The characteristics of emulsions of NiAl-LDHs, o-CNTs and the hybrid in a water-toluene system were investigated by optical microscopy. It was found that among these supports, the hybrid was best emulsified with the narrowest and smallest droplet size distribution (ca. 90 μm) and the largest fraction (95%) of droplet volume. The activity and selectivity for benzyl alcohol oxidation to benzaldehyde increased with interface area for all the emulsions. The Ru/NiAl-LDH-o-CNTs hybrid had the best catalytic performance with the highest values of conversion and selectivity of 96% and 99.9%, respectively.